Stabilization of glyceride oils with carboxymethyl mercaptosuccinic acid



Patented Dec. 15, 1953 STABILIZATION OF GL YCERIDE OILS WITHOABBOXYMETHYL MERQAPTOSUCCINIO ACID W. Schwab, Patricia M. 'Cooney, andCyril 1).. Eva s. P or a, 111-. ignors to the Unite States of America asrepresented by the Secretary'of Agriculture 1 No Drawing. Applicationoctober 5, 1951, Serial No. 250,008

5Claims. (III, 260 39815) (Granted under Title 35, U. S.

Sec. 266).

A non-exclusive, irrevocable, royalty-tree 1icense in the inventionherein, described, for all governmental purposes, throughout the World,with the power to grant sublicenses for such purposes, is hereby grantedto the Government of the United States of America.

This invention relates to the treatment of glycerid oils or fats andsuch related materials as synthetically produced esters of, long chainfatty acids, and edible compositions comprising fats of. an m l or veetable origi It. re ates. pa t cu a ly to the treatment of such fattysubstances to prevent oxidative deterioration and to increase thestorage life and utility of such fatty substances as food. materials.

Glyceride oils of animal or vegetable origin are known to deterioratemore or less rapidly in storage and to develop off-flavors and odorswhich reduce their utility and value as food materials or as ingredientsin pharmaceutical 'orcosmetic compositions. This. deterioration ismainly due to oxidative processes which are; extremely diflicult tocontrol. Diflicultyof control is due largely to the presence; of smallquantities of metals which act as autoxidation catalysts.

According to this-invention, glyceride oils which contain smallquantities. of metallic constituents of the class which possessesoxidativecatalytic properties are treated to remove such metals or toneutralize their catalytic effect, thus increasing the oxidative,stability of the. oil.

We have discovered that carbozgymethyl mercaptosuccinic-acid,

when added to glyceride oils, or theglyceride oil derivatives previouslymentioned, imparts to; such materials improved-flavor andoxidative'stability. This acid apparently has the ability. to removefrom action the metals such as iron and copper,

which commonly act as autoxidation catalysts.

Code (1952),

,Glyceride oils vary in their naturalstability and a s va n eir co of hm tal impurities. In the case of commercially refined edible oils ofvarious agronomic origins, the iron content has been found to vary asmuch as one hundred told, ranging from 0.03 part per million upward.Likewise, the copper content has been found to vary as. much as tenfold, from 0.01 part per million up to 0.1 part per million. Moreover,the metal equipment with which the oil comes in contact during handlingis believed to contribute somewhat to the heavy metal content of theoil.

According to; our invention, the carboxymethyl mercaptosuccinic acid isadded to the oil at relatively cool temperatures. W prefer to add it, inthe case of refined oils, on the cooling side of the steam deodorizationstep. It is preferable to limit the temperature at which the addition ismadeto below 1:00 Q although higher temperatures may bev employed ifcare taken tov minimize th time at which the oil is held at temperaturesabove C. The addition of the stabilizer is relatively simple, since itis readily dispersible in the oil. -It may be added to the oil inanamount ranging from 0.001 to 0.1 percentbased on the weight of the oil.It is convenient to add the stabilizer inalcoholic solution,subsequently removing the solvent alcohol evaporation. However, a widevariety of means' of. addition is satisfactory andwi-ll readily occur tothose skilled in the art.

In the following examples, samples of oil were deodorized in alaboratory steam deodorizer for 3. hours. at,2l0 C., andwere. treatedwithcarboxymethyl mercaptosuccinic acid onthe coolingl side of thedeodorization step. Control samplescon: taining no stabilizer. were alsosubjected to the tests for purposes of comparison. As aIurther basis,for comparison, oil samples containing added catalyticallyactive metalswere alsoevaluated, both withand without the stabilizer.

A chemicalevaluationbased on the active. oxygen method Swift StabilityTest) was made...

which. providesthe peroxide values, taken. after the samples are blownwith air for 8 hours at.

208 F: These aretermed the. A. O. M..values.

The. oils were also. evaluated ,organoleptically'... The taste panel wascomposed of persons skilled.

Table I Control 0.01% carboxymethy mercaptosuccinic Oil Flavor scoreFlavor score A. O. M.

ltoredt8 At flitorcd 14 gltored t8 ays a ays a ays a 60 0. 60 0 so" No.+0 011 No. Oil No. Oil No. 3, soybean Oil No. 3+0.1 p. p. in. Cu.. OilNo. 4, cottonseed. Oil No. F Oil No. Oil No. 011 No. 011 No.

7, soybean In another series of experiments, three samples of soybeanoil, having a measured A. O. M. value mary of the flavor responsesrecorded for oil No. 7, a superior commercial refined soybean oil.

Table III Oil No. 6 0.017 carboxymethyl mercaptosfecmic acid 011 No. 6,control 011 No. 7

Response Stores 4 Stored 8 Stored 4 Stored 8 Stored 4 Stored 8 0 timedays at days at 0 time days at days at 0 time days at days at 60 C. 60 C60 C. 00 C. 00 0. 60 C.

Bland..." 4 1 1 2 0 0 0 0 0 Buttery... 7 6 3 4 0 0 7 2 0 Beany 3 4 5 3 3l l 3 l Grassy 0 0 2 0 4 2 2 2 0 Bancid 0 2 5 0 (i 3 3 7 7 Paintynn O 00 0 3 4 2 1 7 Metallic 0 1 0 0 1 1 1 0 0 Melon 0 0 0 0 0 0 l 1 0Other..... 0 2 l 2 4 3 2 2 2 of 33.7, were treated with varying amountsof stabilizer in the same manner as the oils of the foregoing series.The A. O. M. values are shown The oils in the foregoing tests may bereplaced by other glyceride oils or fats with similar results; forexample, corn oil, perilla oil, safflower oil, lard, lard oil, ortallow.

A major object in preserving oils against oxidative deterioration is toprevent the development of unpleasant flavors as manifested by the tasteand odor of the oil. Deterioration causes the development of grassy,rancid, and painty flavors. The original fresh oil, on the other hand,usually possesses a bland or buttery flavor, which may be associatedwith one or more fiavors that are characteristic of the particular typeof oil. The stabilizer of this invention is particularly valuable, notonly in suppressing the intensity of the flavor of the oils, as measuredby the flavor scores of Table I, but also in preserving the quality ofthe flavor. The flavor responses, recorded by the taste panel inevaluating oils No. 6 and No. 7 are shown in Table HI, with respect to atypical soybean oil (oil No. 6). The table also includes a sum- Thestabilizing effect or carboxymethyl mercaptosuccinic acid has beenexplained in part in the foregoing specification by the ability of thestabilizer to nullify the deleterious eifects of metal autoxidationcatalysts present in the oil. It is to be understood that this inventionis not limited to such explanation, inasmuch as we have found that thestabilizer is effective in preserving the odor and taste of the oilswithout specific dependence on the presence of autoxidation catalysts.

We claim:

1. In a process for refining a glyceride oil which includes the step ofsteam deodorization, the improvement which comprises adding to the oil0.001 to 0.1 percent carboxymethyl mercaptosuccinic acid subsequent tosaid deodorization at a time during the cooling of the oil from saiddeodorization.

2. The process of claim 1 in which the stabilizer is added attemperatures below C.

3. The process of claim 2 in which the glyceride oil is cottonseed oil.

4. The process of claim 2 in which the glyceride oil is peanut oil.

5. The process of claim 1 in which the glyceride oil is soybean oil.

ARTHUR W. SCHWAB. PATRICIA M. COONEY. CYRIL D. EVANS.

References Cited in the file of this patent UNITED STATES PATENTS Number

1. IN A PROCESS FOR REFINING A GLYCERIDE OIL WHICH INCLUDES THE STEP OFSTEAM DEODORIZATION, THE IMPROVEMENT WHICH COMPRISES ADDING TO THE OIL0.001 TO 0.1 PERCENT CARBOXYMETHYL MERCAPTOSUCCINIC ACID SUBSEQUENT TOSAID DEODORIZATION AT A TIME DURING THE COOLING OF THE OIL FROM SAIDDEODORIZATION.